Posted
by
timothy
on Thursday October 04, 2012 @05:41PM
from the every-time-you-jump-it-screws-things-up dept.

The Bad Astronomer writes "A century ago, astronomers (including Edwin Hubble) discovered the Universe was expanding. Using the same methods — but this time with observations from an orbiting infrared space telescope — a new study confirms this expansion, and nails the rate with higher precision than done before. If you're curious, the expansion rate found was 74.3 +/- 2.1 kilometers per second per megaparsec — almost precisely in line with previous measurements."

Not to be pedantic, but that is an impressive way to misspell 'messureents'.

And yet they calculated the speed of light modified by the expansion of available space to travel through at a potentially non-static rate. I'm sure they didn't make a mistake there either, lol. Okay, here's my amateur astronomer opposition theory: the rest of the universe is gone! IT'S JUST GONE! But we're still receiving light from when it was there. Prove me wrong, lol. See, anyone can make anything up that's unprovable with modern technology.

Unless you have a generic curiosity, don't try to hard to read that, as it is not related to the universe's expansion. The grandparent was just being random or joking. A Hilbert space is just what you get when you treat the set of all continuous functions as a vector space. It has several different possible basis sets of functions you can add up to make any other function, e.g. sine waves via Fourier analysis. Instead of having unit vectors like x, y, and z, you would have unit vectors like sin(x), sin(2x), sin(3x), etc. (which makes it infinite dimensional). The concept is really important to physics, especially quantum mechanics and any where else things like Fourier analysis would be done with some mathematical rigor. But it is not what the universe is expanding into.

The typical analogy used for what the universe is expanding into is like a balloon being inflated, with that being a 2D universe on the surface of the balloon. You could ask about the third dimension it is expanding into, but that is not really relevant (at the moment at least). The only thing that really matters is the curvature of local space (how non-flat any given spot on the balloon is). Short of discovering some new theories unlike what we've seen before or something like brane theory, the equivalent of the 3D dimension in the balloon analogy would be unreachable and meaningless, as it would not be able to affect things in anyway beyond the curvature of the surface.

Correction: There is no space and time that we can determine with any certainty outside our physical universe.

This is imprecise at best. There is no "outside our physical universe", because dimensions becomes meaningless at the border of the universe, so there is nowhere "outside" for other universes to be. If they exist, they don't exist "outside" our universe, at least not in a dimensional sense.

As for time, that is a purely local phenomenon, and we can not determine it even inside our universe, except right here. Every "here" will have its own rate of time.

"In the beginning, God created the heavens and the earth. The earth was without form and void, and darkness was over the face of the deep. And the Spirit of God was hovering over the face of the waters."

I'm also disturbed by your use of the phrase "rate of time." What does that mean, if anything?

For a local observer observing itself, nothing.Time itself bends in the presence of gravity or velocity.

If you sit at A, which is equidistant from B and C, and observe a spaceship close to the speed of light going from B to C, you may observe that the trip took five years. However, the spacefarers aboard the vessel will swear up and down that it only took two years. And you're both right.The travelers who are in a different time frame has a different "rate of time" -- by your clock. Just like you have by

For it to not be true, relativity would have to be completely wrong. Since it's back up by math, and you assertion is backed up by an unwillingness to understand, I'm going to have to side with relativity until you show some evidence other than `It's just no common sense!'.

If from the photon's perspective, it lasted exactly 0 time, then it never existed as all things that have never existed also have existed a time of 0. In one frame of reference, the photon exist, but it does not exist in the other frame of reference.

Black and white thinking meets the limits of conception. *every* concept is wrong. It is a trivial statement. Both the concept, and its black & white categorization as right/wrong, are artefacts of the human brain. And the GP is wrong. From a photons point of view, it has zero lifetime only if it travels through a perfect vacuum. Light travels more slowly otherwise, and then observes "time" and "distance".

Another way of saying is, if a photon was generated in a distance star, and it intersected with

Until we can test our models experimentally (highly unlikely for this particular case), I'd say that "uncertain" is a very precise way to describe it.

being an outside to be uncertain about.

You can't go five feet past the edge of the universe, because there is no space to measure five feet in. There isn't a void outside the universe where other universes can be, because that presupposes that there is a void with spatial coordinates, while those are attributes that belong to our universe.Yes, we want to think of what's beyond, and our intuitive thinking doesn't deal well with models that doesn't represent space as we think of it.

The problem with what you're saying is the word "into". It still suggests that there is some medium into which the universe expands. It's another form of the famous Hawking problem "What's north of the north pole?" If there is nothing, then the universe is not expanding into it. It is simply expanding.

As much as anything, it is a problem that while expressable mathematically, is, at least to most peoples' brains (mine included) something impossible to imagine. It is just another way in which our common every day perceptions of the world around us don't model every aspect of reality well.

Another good question is if a galaxy one megaparsec away (that is, 3.26 million light years) is be moving away from us at 74.3 km/sec.How is it that a galaxy two megaparsecs away is moving at twice that speed, or 148.6 km/sec. That doesn't seem to make sense. Is the theory that the universe is expanding more quickly at the edge than at the center or are we at further out looking in?

Due to expansion, the speed of objects accelerating away from us is proportional to the distance from us. So according to this, an object at 1 megaparsec from us will be receding at 74.3 km/s, while an object at twice the distance will be moving twice as fast.

That can't be right. The universe is about 14,000 megaparsecs in radius, even if we were at the exact center that would have things traveling outward at 1.04E9 m/s or 3.46c. I'm reasonably certain they're not claiming FTL on this one so... Is it actually 74.3 m/s instead of 74.3 km/s? Or is there something else going on here?

Space itself can expand FTL, but anything inside that space is limited to c. This also means that at any given point in the universe, there is a boundary where you can never reach beyond, because the space itself is expanding away FTL, so you can never catch up to observe anything beyond that boundary...

Something I've been wondering about, but never knew quite where to ask. (Maybe this isn't the place either, but I'll give it a shot.)

i understand (or at least parse the semantic meaning) that the speed of light through space is fixed, and space can expand fasterthan that. Normally, it seems that the speed of information transmission is also tied to the speed of light, mainly I presume, because paradoxes would arise if it weren't. But can information travel across space at an effective speed uninfluenced by the expansion of space without causing paradoxes? Is it possible that information could still reach us even if light could not?

i understand (or at least parse the semantic meaning) that the speed of light through space is fixed, and space can expand fasterthan that. Normally, it seems that the speed of information transmission is also tied to the speed of light, mainly I presume, because paradoxes would arise if it weren't. But can information travel across space at an effective speed uninfluenced by the expansion of space without causing paradoxes? Is it possible that information could still reach us even if light could not?

FIrst off, don't worry about paradoxes, because physics doesn't. As much as it may hurt our brains, according to Tippler's solution for an infinitely long cylinder, Feynman diagrams and other solutions for Einstein's equations for general relativity, it seems that the physics doesn't bear out paradoxes. However, many of these cases are so extreme that we doubt we'll ever see them and its a safe bet to even say they are not actually possible (although nothing prohibits them according to the physics I have se

If I recall, one of the principles around c is that two things may not move apart faster than c, either. So if you have an observer with a lantern on a train moving 60mph, the light moves away from the observer at c. But! It also moves away from the train platform at c, not c + 60mph

Now as I see it, what is being described is that the universe (spacetime) is the train in my scenario. How could you then account for the rate of expansion from the perspective of two individuals, one at each "e

Space itself can expand such that the objects (events?) within it are moving apart at faster than c. Any two objects separating faster than c can't measure that -- they cannot pass any signal between them. Any light (or other signal) which leaves one will be redshifted away to nothing before it gets to the other. They are outside each other's observable universe. I'm pretty sure this has to handled using General Relativity, I don't think Special Relativity has any concept of expanding or contracting space-time. Space-time described by Special Relativity is flat and static.

I'm open to discussion, but I'd say there is a flaw in your example -- if points A and B are truly 'at rest' relative to each other then by definition the distance between them is not growing (no velocity induced redshift). I think you are trying to use the definition of 'rest' as meaning no "peculiar motion" (astronomical term) on top of the motion imparted up on them by the expansion of space between them. A concrete example would be galaxies observed at a large distance -- they all have a redshift due t

Dang, now I have to go review some GR stuff to go any further. When you get deep into GR, either on cosmological distances or strong gravity fields things get badly non-intuitive. In this particular case I think we will run into the problem of what exactly is meant by "areas of space receding from each other at faster than c". I'll leave with this one question -- if you postulate two objects separating from each other at faster than c due to the cosmological distance between them, and further assert tha

Except I don't think the expansion applies at the galactic level, so anything in a galaxy will still have the whole galaxy with it. Now if you're talking about galaxies themselves as the objects of the universe, then that's likely true.

Just to clarify something that bothers me because so many people seem to believe it despite relativity expressly making it impossible: the universe has no center. Really, look it up. Similarly, the "big bang" does denote an explosion from a specific point.

The center of the observable universe is exactly where I am at this moment. Beyond the observable universe, we have no idea, so we might as well assume that the center of the universe is the same as the observable universe. Me.

In the vein of xkcd-what-if #11 [xkcd.com], I wonder about the physical meaning of kilometers per second per megaparsec. Kilometer and megaparsec are both lengths, so you can divide them out by the conversion factor (1 megaparsec = 3.08567758 × 10^19 kilometers) and then you are left with "per second", i.e., a frequency. A frequency of about 240 billion gigahertz. What, if anything, does that mean?

It helps to actually include the units in your math as "unsolvable variables" that cancel each other out in your conversions. It's a fairly easy way to make sure the math comes out correct. Granted, this extremely rough number is kinda interesting because it is less than 10% off from

From my understanding, speed is relative, so the terms the relation of the two objects, the one being measured from and the one being measured to. As those speeds (relative) approach Light, that is when we can start seeing other interesting effects, like space curving. Space curving is what really boggles the mind, because it is, and isn't curving, depending on what you are looking at, because the "speed" is what bends our perception.

Interestingly, some back of the envelope calculations (using rough numbers... 300000km/s for c, 75km/s/mpc for Hubble's Constant, and 3.25 ly/pc) gives a value of roughly 13 billion light years for the recession velocity to approach c. 13 billion years is also *ROUGHLY* the age of the visible universe.

Hogshead per fortnight (equivalent to m^3/s) is the wrong unit of measurement for expressing the expansion of the universe. I'd go with 2.4 +/- 0.068 exaHz for a whimsical and opaque way of expressing it.

If you want the expansion as a volume you could use m^3/(s*m^3), i.e., rate of volumetric expansion per volume of space. m^3/s just gives you a rate of volumetric expansion, it doesn't say anything about the volumetric expansion being faster if you look at a larger volume, or equivalently, things move faster away from you the further away from you they are, i.e., m/(s*m), which is what Hubble's Law is all about.

You can of course calculate the expansion of af known volume of space e.g. the entire universe* o

Well, there is the dark [slashdot.org] flow [wikipedia.org], a mysterious influence on the motion of distant galaxies whose cause can no longer be observed because it has presumably passed beyond the visible universe. However, we can still see the results of its effect on stuff that is still in the visible universe.

Its things like this that we've confirmed as accurate as much as we can that makes me think the universe isn't expanding at all, we're just able to see more of it all the time. The current size of the universe closely correlates with the speed of light and the time it would have taken that light to reach us... coincidence?

Space itself is supposedly able to expand faster than the speed of light, however I'd like someone to point me to the evidence that this is happening at all.

Light can experience doppler shift like sound can (well, really any wave can see a doppler shift). So if two objects are moving away from each other, light from one to the other will be red shifted. If two objects are moving closer together, the light will be blue shifted.

Since chemicals have known spectral emission/absorption lines, you use that data compared with your observational data of distant objects to figure out the actual shift. Add in some math and you can even figure out

If you shine a laser pointer at the sky (not airplane), the beam leaves earth, and about 14 billion years the beam will reach the farthest galaxies we can see. What happens after another 1000 billion years? Will the beam curve back on itself? Will it slow down and go only at the rate of expansion? But, if the beam just keeps on going at c---it would be beyond the ``visible edge'' of the universe, no? Wouldn't that imply that the `non-visible' real edge of the universe has to expand at least at 'c' or else y

Edwin Hubble was very sceptical about, so called "Big Bang" theory and claimed that there might be different explanation of redshift effect which he observed.

``Astronomer Edwin P. Hubble says that after a six-year study, evidence does not support what we now call the Big Bang theory, according to the Associated Press. “The universe probably is not exploding but is a quiet, peaceful place and possibly just about infinite in size.''''

That doesn't mean he was right. The prevailing opinion at the time was for a static, unchanging universe. And the discovery that it was expanding would have been difficult to reconcile with our understanding at the time. Prevailing opinions do change, albeit sometimes slowly, in the face of mounting evidence.

Seeing as we can not see the edge of the universe from where we are....how can we really tell if yesterday the edge was 1.2 km less then it is today?

Are we saying that all objects are moving away from each other at that rate?Of course not, they have gravity and orbits and all that....so what are they using to gauge the edge of the universe has extended from yesterday?

I am not sure about that, who is to say how much further out the edge of the universe is from the very first galaxy that we may record, or maybe we still have yet to actually be able to see the first galaxy seeing as it is so far away, so we could be way off if we just use the distances between us and the galaxies, vs. the actual measurement of the edge to us...no?

I am no mathematician, but it seems that everything is theoretical at this point in terms of what we THINK we know and what is fact, hence my ori

I know about this, and am very aware that this practice is used, however, I also know they estimate that the distance betwen the earth and say star 1 is at xx km per second, but 2 things pop into question.... can we use the same formula for something that does not behave the same as stars, we are not talking about an actual object moving in space, but we are talking about a virtual(is it really?) edge of the universe, from which we assume on the other is nothingness, therefor could we really say this object